Carbon materials are combined with carbon fibers to prepare composite materials. Such process is known to be effective in order to improve the performance of such materials. For example, carbon fiber/carbon composite materials comprising high-strength carbon fibers are known as CC composite materials. Such materials are superior in specific strength (i.e., strength/density) to conventional metal materials, and thus, the applications of such composite materials are being expanded in various fields. For example, such CC composite materials are used for brake pad materials of automobiles or aircraft.
A variety of techniques for preparing reinforced carbon composite materials have been attempted via dispersion of second-phase particles in carbon materials. While the addition of dispersed particles results in the improved abrasion resistance of composite materials, the added particles sometimes become fracture origins in the materials and disadvantageously deteriorate the strength of the materials. In order to improve both the strength and the abrasion resistance of carbon materials via incorporation of second-phase particles, accordingly, it is necessary that fine second-phase particles be added in an amount required so as to result in a lack of deterioration of the strength of the material. It is necessary to add fine second-phase particles having an average particle diameter of 1 μm or smaller in order to realize satisfactory strength. It is deduced that the second-phase particles with the carbon matrix phase are suitable. Examples of such particles include high-purity metal carbides, such as tungsten carbide, titanium carbide, and silicon carbide, which remain stable without denaturing during the process of producing given members.
Production of fine particles of high-purity metal carbides in a cost-effective manner, however, involves serious technical difficulties. As the diameters of particles of metal carbides become small, dispersion of particles in a material with a carbon matrix phase becomes difficult due to aggregation or other activities. Accordingly, it is technically difficult to homogeneously incorporate such particles in a material with a carbon matrix phase. During the process for producing fine particles with very large specific surface areas, the surfaces of such particles are easily oxidized. Thus, it is practically impossible to prepare composite materials composed of carbon materials and fine particles of high-purity metal carbides.
JP Patent Publication (Kokai) No. 11-130537A (1999) discloses a method for producing a carbon composite material comprising particles of reinforcing metal carbides each with an average particle diameter of 1 μm or smaller dispersed therein, wherein starting powder materials having carbon matrix phases are mixed with at least one kind of metal oxide in advance, the mixture is molded and then calcined, and the calcination product is impregnated with pitch, followed by recalcination. This method is intended to produce carbon composite materials comprising particles of reinforcing, high-purity, and fine metal carbides dispersed therein in efficient and cost-effective manners.
JP Patent Publication (Kokai) No. 11-217267 A (1999) discloses a method for producing two-dimensional fiber-reinforced silicon carbide-carbon composite ceramics comprising forming a formed product comprising silicon powder, a resin as a carbon source, and a two-dimensional fiber-reinforced material into a desired shape, carbonizing the formed product at 900° C. to 1,300° C. in an inert gas atmosphere, impregnating the resultant with a resin, re-sintering the impregnated material at 900° C. to 1,300° C. in an inert gas atmosphere, iterating the resin impregnation and sintering, and finally sintering the material at about 1,350° C. to 1,500° C. in an inert gas atmosphere. This method is intended to readily produce two-dimensional fiber-reinforced silicon carbide-carbon composite ceramics having high strength and complicated shape regardless of high open porosity via impregnation of the ceramics with a resin and the reaction sintering method.